Hi,
You need to select a Azure AD user instead of a Microsoft Account user. If you don't have one you want to use you may create a new user in Azure Active Directory.
In the Azure portal, Azure Active Directory -- Users, Azure AD users will have <yourdomain>.onmicrosoft.com in the Identities column instead of MicrosoftAccount. Similar to screenshot below:
If the above was helpful please click Accept Answer.
Thanks.
-TP